They are more prone to certain types of diseases...not all!! And since our population is 30% blacks and hispanics you cannot compare them to a nation which has a small percentage of blacks and hispanics.
The only way to truly lower costs is lowering the amount of medical visits. A fewer number of medical claims means that insurance companies can lower premiums needed in cash reserves to cover medical bills. Thinking that miraculously prices will drop because it is a government run agency is a falsehood. Physicians and nurses will always be paid top dollar because they have highly specialized roles, medical technology will always be expensive because these are machines we rely on to save lives, and pharmaceutical companies will always produce expensive medication because many of the pills on the market take years to research & create by scientists. And it also takes millions of dollars to go through FDA approval. And if one pill is bad in 20 million bottles then they do a full recall. All of this costs money and always will.